The military is still using morse code

Wireless telegraphy

A 1943 US Army Signal Corps radio operator in New Guinea broadcasting by radio telegraph

Wireless telegraphy or Radiotelegraphy is the transmission of telegraph signals by radio waves. Prior to about 1910, the term wireless telegraph was also used to refer to other experimental technologies for transmitting telegraph signals without wires, such as: B. Electromagnetic Induction and Earth Line Telegraph Systems.

Radiotelegraphy was the first means of radio communication. The first practical radio transmitters and, which were invented by Guglielmo Marconi in 1894–1895, used radio telegraphy. It continued to be the only type of radio transmission in the first decades of radio known as the "era of wireless telegraphy" until World War I when amplitude modulation (AM) radio telephony enabled the transmission of sound (audio) by radio. In radiotelegraphy, information is transmitted by pulses of radio waves of two different lengths called "dots" and "dashes" that spell out text messages, usually in Morse code (frequency shift keyed

knows. Radiotelegraphy was used for person-to-person long distance calls. and military text communication in the first half of the 20th century. It became a strategically important skill during both world wars as a nation without remote radio stations could be isolated from the rest of the world by an enemy severing its submarine telegraph cables. From around 1908, powerful transoceanic radio telegraph stations were sending commercial telegram traffic between countries at speeds of up to 200 words per minute.

Radiotelegraphy has been transmitted through various modulation methods throughout its history. The primitive spark gap transmitters that were in use until 1920 sent attenuated waves that had a very wide bandwidth and tended to interfere with other transmissions. This type of emission was banned until 1930. The vacuum tube (valve) transmitters, which came into use after 1920, sent code through pulses of unmodulated sinusoidal carrier wave continuous waves (CW), which are still used today. In order to receive CW transmissions, the receiver needs a circuit called a beat frequency oscillator (BFO). The third type of modulation, Frequency Shift Keying (FSK), was mainly used by radio tele types. Morse code radio telegraphy was gradually replaced by radio teletype networks (RTTY) in most high volume applications until World War II. Today it is almost out of date, the only remaining users are the radio amateur community and some limited military training in case of emergency.

Overview

Amateur radio operator, the Morse code

Sends wireless telegraphy or radiotelegraphy, commonly referred to as CW transmission (perm), ICW transmission (interrupted perm) or on-off keying and designated with The International Telecommunication Union as emission type A1A is a radio communication method in which the sending operator has a - Switch manipulated as

Although this type of communication has largely been replaced by other means of communication since its inception over 100 years ago, it is still used by amateur radio operators as well as some military services. California also has a CW coast station, KSM, which is mostly run by volunteers as a museum and occasionally contacts are made with ships. Radio beacons, especially in the air traffic service, but also as "placeholders" for commercial ship-to-shore systems, also send Morse signals, but at a very slow speed. Wireless telegraphy is still widely used today by amateur radio hobbyists where it is commonly referred to as radio telegraphy, perm, or just plain CW. However, his knowledge is not required to receive an amateur license class.

Non-radio methods

Efforts to find a way to transmit telegraph signals without wires grew out of the success of electrical telegraph networks, the first instant telecommunication systems. Developed from the 1830s onwards, a telegraph line was a person-to-person text messaging system that consisted of several telegraph offices connected by an overhead cable that was on top of telegraph poles

By the 1860s, the telegraph was the standard method of sending the most urgent commercial, diplomatic, and military messages, and the developed world had established continental telegraph networks where submarine telegraph cables allowed telegraph messages to be sent across seas. However, a telegraph line connecting distant stations was very expensive to install and maintain, and cables could not reach some places such as ships at sea. Inventors realized that a way to send electrical pulses of the Morse code between different points without connecting cables could revolutionize communication.

The successful solution to this problem was the discovery of radio waves in 1887 and the development of practical transmitters and receivers for radio telegraphy by about 1899, which are described in the next section. However, it was preceded by a 50-year history of ingenious, but ultimately unsuccessful, experiments by inventors to achieve wireless telegraphy in other ways.

Underground, water and air pipelines

Several wireless electrical signaling schemes based on the (sometimes flawed) idea that electrical currents could travel long distances through water, soil, and air for telegraphy were investigated before practical radio systems became available.

The original telegraph lines used two wires between the two stations to create a complete circuit or "loop". In 1837, Carl August von Steinheil of Munich, Germany determined that by connecting one leg of the apparatus to each station with metal plates in which he could remove one wire and use a single wire for telegraphic communication. This led to speculation that it might be possible to eliminate both wires and therefore transmit telegraph signals over the ground without wires connecting the stations. Other attempts have been made to conduct electricity through bodies of water, for example to span rivers. Prominent experimenters in this direction were Samuel FB Morse in the United States and James Bowman Lindsay in Great Britain, who in August 1854 was able to demonstrate the transmission over a mill dam from a distance of 457 meters.

Tesla's explanation in the 1919 edition of Electrical Experimenter how he thought his wireless system would work

US inventors William Henry Ward (1871) and Mahlon Loomis (1872) developed electrical conduction systems based on the false assumption that there is an electrified atmospheric layer that is accessible at low altitude. They thought atmospheric electricity coupled with a return path using "earth currents" would enable wireless telegraphy and power the telegraph, eliminating the need for artificial batteries. A more practical demonstration of wired wireless transmission was found in the 1879 Amos Dolbear magneto-electric telephone, which transmitted the earth wire a quarter of a mile away.

In the 1890s inventor Nikola Tesla was working on a wireless air and ground conduction system for electrical power transmission, similar to the one Loomis designed for wireless telegraphy. Tesla's experiments had erroneously led him to conclude that he could use the entire globe of the earth to conduct electrical energy, and his large-scale application of his 1901 ideas, a high-voltage wireless power plant now called the Wardenclyffe Tower, lost funding and was given up after a few years.

It was eventually found that telegraphic communication using earth conductivity was limited to impractically short distances, as was communication over water or between trenches during World War I.

Electrostatic and electromagnetic induction

Thomas Edison's 1891 patent for a wireless ship-to-shore telegraph using electrostatic induction

Both electrostatic and electromagnetic induction were used to develop wireless telegraph systems that found limited commercial application. In the United States in the mid-1880s, Thomas Edison patented an electromagnetic induction system that he called "grasshopper telegraphy" that enabled telegraph signals to skip the short distance between a moving train and parallel telegraph wires to get to the tracks. This system was technically but not economically successful, as train travelers showed little interest in using an on-board telegraph service. During the Great Blizzard of 1888, this system was used to send and receive wireless messages from trains buried in snowdrifts. The disabled trains were able to maintain communications through their Edison wireless induction telegraph systems, possibly the first successful use of wireless telegraphy to send emergency calls. Edison would also help patent a ship-to-shore communication system based on electrostatic induction.

The most successful developer of an electromagnetic induction telegraph system was William Preece, Chief Engineer of the Post Telegraphs of the General Post Office (GPO) in the United Kingdom. Preece first noticed the effect in 1884 when overhead telegraph wires mistakenly carried messages over buried cables on Grays Inn Road. Tests in Newcastle managed to send a quarter mile with parallel wire rectangles. When testing the Bristol Channel in 1892, Preece was able to telegraph over gaps of about 5 kilometers (3.1 miles). However, his induction system required great lengths of antenna wire, many kilometers long, at both the transmitting and receiving ends. The length of these transmit and receive wires had to be roughly as long as the width of the water or land to be spanned. For example, in order for the Preece station to span the English Channel from Dover, England to the coast of France, approximately 30 miles (30 miles) of wires must be transmitted and received. 48 kilometers) along the two coasts. These facts made the system impractical on ships, boats, and common islands much smaller than Britain or Greenland. Because of the relatively short distances a practical preece system could travel, it had few advantages over underwater telegraph cables. .

Radio telegraphy

British postal engineers inspect the Marconi sender (center) and receiver (below) on Flat Holm, May 1897
Typical commercial radio telegraph receiver from the first decade of the 20th century. The "dots" and "dashes" of the Morse code were recorded in ink on paper tape with a siphon recorder (left).
Example of a transatlantic radiotelegraph message recorded on paper tape in 1920 at the New York RCA receiving center. The translation of the Morse code is given below the ribbon.

For several years from 1894, the Italian inventor Guglielmo Marconi worked on adapting the newly discovered phenomenon of radio waves for communication, which up to this point had essentially transformed a laboratory experiment into a useful communication system and with them built the first radio telegraphy system. Preece and the GPO in Great Britain initially supported and supported Marconi's experiments, which were carried out in Salisbury Plain from 1896. Preece had been convinced of the idea through his experiments with wireless induction. However, support was withdrawn when Marconi formed the Wireless Telegraph & Signal Company. GPO lawyers determined that the system was a telegraph within the meaning of the Telegraph Act and therefore fell under the postal monopoly. This didn't seem to stop Marconi. After Marconi sent wireless telegraph signals across the Atlantic in 1901, the system was used for regular communications including ship-to-land and ship-to-ship communications.

With this development the wireless telegraphy was meant radio telegraphy, Morse code, which is transmitted by radio waves. The first radio transmitters, primitive spark gap transmitters, which were used until the First World War, could not transmit speech (audio signals). Instead, the operator would send the text message on a telegraph key which turned the transmitter on and off and generated short ("dot") and long ("dash") pulses of radio waves, groups of which included the letters and other symbols of the Morse code. At the receiver, the receiving operator could hear the signals as musical "beeps" in the headphones, which would translate the code back into text. By 1910, "Hertzian wave" communication was commonly referred to as "radio" and the term "wireless telegraphy" was largely replaced by the more modern term "radio telegraphy".

Continuous waves (CW)

The primitive spark gap transmitters that were in use until 1920 and transmitted by a method of modulation called dampened waves. As long as the telegraph button was pressed, the transmitter generated a series of transient pulses of radio waves that repeated themselves at an audio rate, usually between 50 and several thousand Hertz. In the headphones of a receiver this sounded like a musical tone, a rasp or a hum. The Morse code "dots" and "dashes" sounded like beeps. Attenuated waves had a wide frequency bandwidth, which means that the radio signal was not a single frequency, but occupied a wide frequency band. Attenuation wave transmitters had a limited range and interfered with the transmission of other transmitters on neighboring frequencies.

After 1905, new types of radiotelegraph transmitters were invented that transmit codes using a new method of modulation: continuous waves (CW) (referred to as Emission by the International Telecommunication Union, type A1A). As long as the telegraph button was pressed, the transmitter generated a continuous sine wave with a constant amplitude. Since the entire energy of the radio wave was concentrated on a single frequency, CW transmitters could continue to transmit with a certain power and also caused practically no interference in transmissions on neighboring frequencies. The first transmitters that could generate continuous waves were the arc converter (Poulsen arc), invented in 1903 by the Danish engineer Valdemar Poulsen, and the Alexanderson generator. invented 1906-1912 by Reginald Fessenden and Ernst Alexanderson. These slowly replaced the spark transmitters in high-performance radio telegraphy stations.

However, the radio receivers used for attenuated waves could not receive continuous waves. Since the CW signal generated when the button was pressed was only an unmodulated carrier wave, there was no sound in the headphones of a receiver. In order to receive a CW signal, a way had to be found to make the Morse code carrier wave pulses audible in a receiver.

This problem was solved in 1901 by Reginald Fessenden. In its "heterodyne" receiver, the incoming radiotelegraph signal is mixed in the detector crystal or in the receiver's vacuum tube with a constant sine wave generated by an electronic oscillator in the receiver called a beat frequency oscillator (BFO). The frequency of the oscillator is opposite the frequency of the radio transmitter . The two frequencies are subtracted in the detector, and a beat frequency (superposition) is generated at the difference between the two frequencies: . If the BFO frequency is close enough to the frequency of the radio station, the beat frequency is in the range of the audio frequency and can be heard in the receiver's headphones. During the "dots" and "dashes" of the signal, the beat tone is generated while there is no carrier between them, so no tone is generated. This means that the Morse code can be heard as a musical "beep" in the headphones.

The BFO was rare until the invention of the first practical electronic oscillator in 1913, Edwin Armstrong's vacuum tube feedback oscillator. After that time, FBOs were a standard part of RT receivers. Every time the radio was tuned to a different station frequency, the BFO frequency had to be changed too, so the BFO oscillator had to be tunable. In later superheterodyne receivers from the 1930s onwards, the BFO signal was mixed with the constant intermediate frequency (IF) generated by the superheterodyne's detector. Therefore the BFO could be a fixed frequency.

Continuous wave vacuum tube transmitters replaced the other types of transmitters with the availability of power tubes after the First World War because they were cheap. CW became the standard method for transmitting radio telegraphy in the 1920s, muted wave spark transmitters were banned in 1930, and CW is used to this day. Even today, most communication receivers made for use in shortwave communication stations have FBOs.

The RT industry

During World War I, balloons were used to quickly raise wire antennas for military radiotelegraph stations. Balloons on Tempelhofer Feld, Germany, 1908.

The International Radiotelegraph Union was unofficially founded in 1906 at the first International Radiotelegraph Convention and incorporated into the International Telecommunication Union in 1932. When the United States entered World War I, private radiotelegraph stations were banned, ending the work of several pioneers in the field. By the 1920s, there was a worldwide network of commercial and government radiotelegraphic stations, and widespread use of radiotelegraphy by ships for both commercial and passenger messaging purposes. Sound transmission (radio telephony) began to replace radio telegraphy for many applications in the 1920s and made radio transmission possible. Wireless telegraphy continued to be used for personal business, government, and military person-to-person communications, such as: B. Telegrams and diplomatic communication, and developed into the radio type networks. The ultimate implementation of wireless telegraphy was telex using radio signals, which was developed in the 1930s and for many years was the only reliable form of communication between many distant countries. The most advanced standard, CCITT, automated both the routing and encoding of messages through shortwave transmissions.

Morse code radio telegraphy is now obsolete for commercial use due to more modern text transmission methods. On board, the computer and the satellite-based GMDSS system have largely replaced Morse as a means of communication.

Regulation of radio telegraphy

Continuous wave (CW) Radio telegraphy is regulated by the International Telecommunication Union (ITU) as emission type A1A.

The US Federal Communications Commission issues a lifetime commercial radiotelegraph operator license. This requires passing a simple written test on regulations, a more complex written test on technology, and demonstrating Morse code reception at 20 words per minute in clear text and 16 wpm code groups. (Credits are given for top-class amateur licenses acquired under the old 20 wpm requirement.)

gallery

  • Guglielmo Marconi, the father of radio-based wireless telegraphy, was awarded one of his licenses in 1901. First radio transmitters (right) and receivers (left)

  • German troops set up a radio field telegraph station during the First World War

  • German officers and troops occupied a radio field telegraph station during the First World War

See also

References and Notes

General
Quotes

further reading

Listed by date [at the latest at the earliest]

External links

  • John Joseph Fahie, A History of Wireless Telegraphy, 1838–1899: Including Some Bare-Wire Proposals for Sub-Aqueous Telegraphs, 1899 (first edition).
  • John Joseph Fahie, A History of Wireless Telegraphy: Including Some Bare-Wire Proposals for Sub-Aqueous Telegraphs, 1901 (second edition).
  • John Joseph Fahie, A History of Wireless Telegraphy: Including Some Proposals for Sub-Aqueous Telegraphs, 1901 (second edition, in HTML format).
  • Alfred Thomas Story, The history of the wire less telegraphy, 1904 [1]
  • James Bowman Lindsay A brief biography of his electric lamp and telegraphic endeavors.
  • Sparks Telegraph Key Review
  • Principles of Radiotelegraphy (1919)